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Color and Light · entry 28 of 52
A rainbow is actually a full circle, but the ground usually hides the lower half.
The longer version
The bow is a cone of directions centred on the point directly opposite the sun, and a cone meets flat ground as an arc. With nothing blocking the view, that arc closes into a complete ring at a fixed angular distance from the antisolar point.
From an aircraft with the sun high and rain below, the full circle is easy to see, and it is a common sight for pilots. From the ground, the horizon cuts it off, so people grow up believing a rainbow is intrinsically half a circle rather than a full one that is simply interrupted.
Where this entry sits
These facts explore how light behaves and how human eyes turn it into the colors we see. Along the way you meet rainbows, prisms, mirrors, shadows, lasers, and optical tricks that fool our vision every day. The full list sits on the Color and Light page, where every entry is listed in order.
More From Color and Light
Eight more entriesDouble rainbows happen when light reflects twice inside each droplet, reversing the color order.
Read 30You never see a rainbow from directly overhead because the geometry requires looking away from the sun.
Read 31Red light bends least through glass, while violet light bends the most.
Read 32The color orange takes its name from the fruit, which had the word first.
Read 33Purple and violet describe similar hues, though violet refers to a single wavelength of light.
Read 34Many languages have fewer basic color words than English, sometimes grouping blue and green together.
Read 35Turquoise sits between blue and green on the spectrum and is named after a gemstone.
Read 36Gold and silver describe metallic surface appearances rather than one particular wavelength of light.
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